This invention is directed to a serum transfer cup for holding a relatively small amount of blood serum poured from a blood collection tube.
Blood collection tubes are made in a variety of different sizes, such as 13 mm diameter through 17 mm diameter, and in different lengths that range from 75 mm to over 100 mm. Two popular size blood collection tubes in general use are 13 mm and 16 mm diameter tubes having a length of 75 mm, such as manufactured by Becton-Dickenson.
When a lab draws whole blood from a patient it is usually collected in a standard blood collection tube. The standard blood collection tube with whole blood is generally spun in a centrifuge to separate red blood cells from serum. A gel separator that is provided in the blood collection tube maintains the serum separate from the red blood cells after the centrifuge operation. Thus when the blood collection tube with the whole blood is spun, the serum rises above the gel separator and the red blood cells remain below the gel separator.
The separated serum in the blood collection tube is the material that is used for performing test assays.
In an automated assay system an aspiration/dispensation probe is directed into the blood collection tube to aspirate serum. After several aspirations of serum are taken from the collection tube the serum level will recede and eventually come very close to the gel separator. If further serum aspiration is undertaken when the serum level is close to the gel separator there is a possibility that the aspiration probe may become clogged with gel.
In order to conserve serum when the serum level is in close proximity to the gel separator and not risk clogging of the aspiration probe a technician will usually pour serum from the blood collection tube into a smaller container. Although the volume of serum in the smaller container is essentially the same as it was in the blood collection tube, the column height of serum in the smaller container is increased because the smaller container has a smaller diameter than the blood collection tube. It should be noted that only the serum is poured from the blood collection tube to the smaller container or serum transfer cup.
The blood collection tube usually has a bar code label that identifies the patient from whom the blood was drawn. The serum transfer cup generally does not have a bar code label. Thus, after the serum is poured from a blood collection tube into the serum transfer cup the serum transfer cup is nested back in the open end of the blood collection tube to maintain integrity of patient identification with respect to serum in the serum transfer cup.
In summary, the blood collection tube which has whole blood is spun down to separate serum from red blood cells. The separated serum is usually aspirated down to a level where it is then poured into a serum transfer cup. The serum transfer cup is nested in the blood collection tube to permit continued use of the serum without losing patient identification. The serum transfer cup conserves the serum by rearranging it into a usable column of fluid that facilitates further aspiration of small amounts of serum by an aspiration probe. In many instances use of the serum transfer cup eliminates the need to redraw blood from a patient in order to obtain more serum.
A known serum transfer cup is sold under the trade designation Ezee-Nest®. However, in an automated assay system that uses robotics to move blood collection tubes around the assay system the Ezee-Nest® serum transfer cup may rattle or vibrate inside the blood collection tube, which can result in spillage of serum from the serum transfer cup. A serum spill may require redrawing of whole blood from a patient, and can also contaminate blood samples in the nearby blood collection tubes within the automatic assay system.
It is thus desirable to provide a serum transfer cup that can fit with minimal clearance in a blood collection tube to minimize or prevent rattling or vibration of the serum transfer cup while the blood collection tube is being transported in an automated assay system.
During automatic liquid level sensing there must be a predetermined minimum height of serum underneath the tip of the probe. If a probe goes below the minimum liquid level height there is a danger of mis-sensing the liquid level or mis-aspirating the serum, whereby an incomplete aspiration can occur in which some air is aspirated instead of a complete serum aspiration.
When an expected volume of serum that is critical for a test assay is not aspirated and some air is aspirated instead of serum, there will be an erroneous assay. Therefore it is desirable to have a predetermined minimum level of serum beneath the last viable serum aspiration so that the probe does not mis-aspirate serum or crash into the bottom of a serum container and cause damage to the probe.
It is also desirable to provide a serum transfer cup that makes maximum use of relatively small amounts of serum remaining in a blood collection tube, provides a safe clearance height up from the bottom of the inside of a serum transfer cup and allows an aspiration probe to have a safe clearance of at least a millimeter on either side of the probe to the closest wall of the serum transfer cup.
It is also desirable to have one serum transfer cup that can fit into two different size blood collection tubes, such as a 13 mm and a 16 mm collection tube, without troublesome rattling or vibration.